Case IH 381 – ENG (Engine Controller / Engine ECU): Error detected in cold start relay 1

The engine control system has detected an electrical fault—such as an open circuit, short circuit, or abnormal voltage—in the primary relay circuit responsible for activating the cold start system (typically the intake manifold grid heater or thermostart system).

• MX Magnum
• STX Steiger
• Steiger
• Magnum
• Maxxum (e.g., 115, 125, 135, 145, 150)
• Puma
• Vestrum
• Versum
• CX series
• 580M Series 2 Loader Backhoes
• 580SM Series 2 Loader Backhoes
• Crawler Dozers (e.g., 550H, 650K)
• rough-terrain forklifts

1. 1

   Verify operating conditions: Ensure ambient/coolant temperatures are below 60°F, as the grid heater system only activates under these conditions.

2. 2

   Test the heater element: Measure resistance of the grid heater element with a multimeter (should be ~0.001 ohms). An open circuit indicates a burnt-out heater element, not the relay.

3. 3

   Check relay power: Verify the relay receives constant 12V power from the battery at the primary heavy-gauge terminal.

4. 4

   Check ECM signal: Verify the Engine ECU successfully grounds the relay's control circuit when the ignition key is turned to the 'ON' position during a cold start.

5. 5

   Visually inspect the relay terminals, wiring harness, and connectors for broken locking clips, loose connections, or electrical arcing damage.

1. 1

   Disconnect Power

   Always disconnect the negative battery cable before servicing high-amperage electrical components to prevent short circuits.

2. 2

   Locate the Relay

   Locate the cold start relay, which is typically mounted on the firewall, near the main fuse/relay panel, or adjacent to the engine intake manifold.

3. 3

   Remove Connections

   Carefully label and remove the electrical connections. This usually includes two heavy-gauge cables (battery power and heater feed) and the smaller ECM control wires.

4. 4

   Dismount the Relay

   Unbolt the relay housing from its mounting bracket.

5. 5

   Install the New Relay

   Secure the new OEM relay to the mounting bracket.

6. 6

   Reconnect Wiring

   Reattach all electrical terminals. Ensure the connections are clean and tightened securely to prevent future arcing.

7. 7

   Test the System

   Reconnect the battery. Turn the ignition key to the "ON" position (without cranking the engine). You should hear an audible "click" from the relay, and the "Wait to Start" indicator on the dash should illuminate steadily before timing out.